JPH0571357B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring welding power applied to a welding part of a welding device in high-frequency induction welding.

[Prior art]

To manufacture ERW pipes, a continuously fed metal plate is bent into a predetermined diameter to form an open pipe with edges facing each other, and the pipe is inserted into a high-frequency induction coil, and lateral pressure is applied using squeeze rolls. In addition, the edges are welded together using high frequency. By the way, when performing high-frequency induction welding using a vacuum tube as the oscillation tube that oscillates high-frequency waves, the operator uses the anode DC voltage and anode DC current of the oscillation tube as indicators, as well as checking the welding flame color and bead shape. The heat input is controlled to match the material, dimensions, etc. of the material to be welded.

In addition to the method of controlling heat input or welding conditions, there is also a method for measuring the output power of high-frequency welding equipment.
A method of measuring the effective value of the output voltage, the effective value of the output current, and the phase difference between the output voltage and the output current has been proposed (Japanese Patent Application Laid-Open No. 59-24585). A method of determining welding power by measuring the difference between traveling wave power and reflected wave power between the two has been proposed (Japanese Patent Application Laid-open No. 44752/1983).

[Problem that the invention seeks to solve]

As mentioned above, the anode DC voltage of the oscillator tube was used as an index by the operator to set the heat input or welding conditions.
Since the anode DC current is the input of the welding device, if the efficiency of the welding device changes, the output of the welding device will change and the welding conditions will not be constant. Furthermore, this type of welding apparatus that uses a vacuum tube as the oscillation tube has low efficiency, for example, the oscillation tube efficiency is 60 to 80%, and the overall efficiency is about 50%. This efficiency varies greatly depending on load conditions such as the distance between the heating coil and squeeze roll installed on the ERW tube manufacturing line, the butting angle of the steel strip, the thickness of the material to be heated, and the size of the outer diameter. . This can be compensated for by adjustment based on the operator's skill and intuition, but there is a problem that stable welding cannot be performed.

On the other hand, in the method proposed in Japanese Patent Laid-Open No. 59-24585, it is difficult to accurately measure the output voltage and the phase difference between this and the output current. In other words, the output voltage is high, making it extremely difficult to measure accurate instantaneous values, and the welding power is 50kHz to 1000kHz.
This is because measurement of the phase difference between the output voltage and the output current requires measurement of extremely short periods on the order of nanoseconds, which makes more accurate measurement difficult. This also applies to the patent publication No. 52-44752.

An object of the present invention is to provide a method for measuring welding power that can obtain welding power during high-frequency welding with high precision using a general-purpose calculation device and obtain a stable welding state.

[Means for solving problems]

In view of the above-mentioned problems, the present invention has been developed to convert the welding power of a high-frequency welding device into a high-frequency voltage at the input side of a resonant circuit to which an oscillation output is given, and a high-frequency current within one period of the pulsating voltage applied to the resonant circuit. After temporarily storing the data sampled over a predetermined period at each time point, that is, the high-frequency voltage and high-frequency current that are the oscillator output, in a storage device, the stored data is sequentially calculated by a calculation device to perform welding with high precision. The present invention proposes a welding power measuring method that can measure electric power and keep welding conditions stable at all times.

A welding power measuring method for a high-frequency welding device according to the present invention is a welding power measuring method for a high-frequency welding device that performs welding by oscillating a high-frequency oscillator, which comprises a resonant circuit to provide the oscillator output, The high frequency voltage and high frequency current on the input side are sampled over a predetermined period at different times within one cycle of the pulsating voltage applied to the resonant circuit, the sampled data is stored in a storage device, and the data of the stored measurement values is stored. It is characterized in that the information is sequentially read out and transmitted to a computing device, and the computing device calculates the welding power.

[Effect]

The high-frequency voltage and high-frequency current, which are the oscillator outputs, are sampled at the input side of the resonant circuit over a predetermined period at different times within one cycle of the pulsating voltage applied to the resonant circuit. The sampled data is temporarily read into the storage device. The storage device inputs the read sampling data to the calculation device, and the calculation device performs calculations based on the sampling data from the storage device to measure the welding power. This eliminates the need for a calculation device that performs calculations at high speed. Furthermore, welding power during high-frequency welding can be measured with high precision.

〔Example〕

First, a welding apparatus for carrying out the welding power measuring method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a high frequency welding device using a vacuum tube as an oscillator.

In FIG. 1, an oscillator 1 is a vacuum tube that performs a class C amplification operation, and applies a plate DC voltage Ep consisting of a high DC voltage of about 10 to 15 kV to a plate P of the oscillator 1.

In addition, a coupling capacitor (blocking capacitor) 6 is connected between the plate P and the cathode K of the oscillator 1, and a resonance capacitor is connected to the resonance coil L.
A resonant circuit (tank circuit) 2 in which a series circuit with C ₁ and C ₂ is connected in parallel is connected, and a voltage divider circuit formed by connecting capacitors 3 and 4 in series in parallel with the resonant capacitor C ₂ is connected. has been done. The connection point of capacitors 3 and 4 is connected to grid G of oscillator 1, and voltage dividing capacitors 3 and 4 are connected from resonant circuit 2.
A signal fed back by the grid G is given to the grid G. Further, a bias voltage is applied to the grid G by a grid resistor 5. This causes oscillator 1
The circuit oscillates due to the switching operation synchronized with the grid AC voltage, that is, the resonant frequency of the resonant circuit 2 including the load, and usually supplies high frequency energy to the resonant circuit 2 at a frequency of 50 to 1000 kHz.

The welding power Pw is the product of the plate high-frequency current ip obtained by the current transformer CT and the plate high-frequency voltage ep applied to the resonant circuit 2, and becomes as shown in equation (1).

Pw=ip・ep...(1) A one-turn secondary coil La is linked to the resonant coil L of the resonant circuit 2, and both ends thereof are connected to the aforementioned high-frequency induction coil (not shown), The high-frequency power energy of the resonant circuit 2 is applied as welding power Pw to a welding part (not shown).

7 is a high frequency current measuring device that measures the plate high frequency current ip using a current transformer CT, and 8 is a high frequency voltage measuring device that measures the plate high frequency voltage ep from both ends of the resonant capacitor C. 9 is a storage device that temporarily stores measurement values measured by the high frequency current measuring device 7 and the high frequency voltage measuring device 8;
The measurement data stored in the storage device 9 is transmitted to the arithmetic device 10, and the arithmetic device 10 processes the measurement data to obtain the welding power Pw. The sampling speed for reading measured values into the storage device 9 is set to 1 to 50 nsec to read the fundamental wave component and high frequency component of the plate high frequency voltage of the oscillator 1 with high accuracy.

Next, a procedure for measuring welding power in this high frequency welding apparatus will be explained with reference to FIGS. 2 to 4. Figure 2 is a timing chart showing the process from high frequency voltage sampling to calculation, and Figure 3 is a waveform diagram of the plate high frequency voltage within the sampling period.
Figure 4 shows high frequency voltage 1 to explain calculation operation.
It is a waveform diagram for cycles.

The high frequency voltage applied to the resonant circuit 2 has a peak value of 300 Hz or 360 Hz as shown in Figure 2 because the plate DC voltage Ep of the oscillator 1 is given a pulsating voltage obtained by rectifying the 50 Hz or 60 Hz AC voltage. Ta
It changes like an HF waveform. In other words, the welding power for high-frequency welding changes slightly.

Therefore, in order to obtain such welding power with high precision, approximately one cycle in which the peak value of the high frequency voltage changes, that is, the average period of 300Hz and 360Hz.
At timings A, B, C, and D set at intervals of 90 electrical degrees within a period of 3 msec, high-frequency voltage is sampled within a period of 20 μsec for each timing. During this sampling period, if the high frequency voltage is 200 kHz, the peak values of four cycles can be measured as shown in FIG. 3, and the sampled measurement values are read into the storage device 9. Then, the measurement data 10a read into the storage device 9 is controlled by a control signal 10b given in accordance with the calculation speed by the calculation device 10.
The data is transmitted to the arithmetic unit 10 over 40 msec, and such measurement value sampling and data transmission are repeated five times.

In other words, the peak values of 20 waves (20 cycles) of the high frequency voltage are sampled within 215 msec of the 50 msec calculation cycle. and the rest
Calculation is performed within 285msec. This measurement cycle of 500 msec was determined based on the responsiveness when displaying calculation results using a normal pointer-type meter.

The calculation by the calculation device 10 is performed by calculating the peak value of each wave (for one cycle) of the high frequency voltage as shown in FIG.
Find Vp and −Vp, respectively. Thereafter, the average value of the peak values of eight high-frequency voltage waves of the measurement data obtained by one sampling is calculated, and this is multiplied by 1/√2 to obtain the effective value of the high-frequency voltage. Further, similar to the processing operation for obtaining the effective value of the high-frequency voltage, the processing operation for obtaining the effective value of the high-frequency current is performed in parallel. Finally, the welding power Pw is determined by the above-mentioned calculation of Pw=ip·ep, and this value is temporarily latched to indicate the welding power during welding using a pointer type meter (not shown) or the like.

In this way, the data obtained by sampling the high-frequency voltage and high-frequency current of the oscillator output, which is high-frequency welding power, is temporarily stored in the storage device 9, so the arithmetic device 10 can import and perform calculations regardless of the sampling speed. , a general-purpose arithmetic unit can be used.

In addition, since the peak values of the high-frequency voltage and high-frequency current are sampled over a predetermined period at different times within one cycle of the pulsating voltage applied to the resonant circuit,
Many peak values of high-frequency voltages and high-frequency currents can be determined, and high-frequency voltages whose peak values are changing can be averaged, and welding power can be detected with high precision to stabilize the welding state. In addition, since the peak values of the high-frequency voltage and high-frequency current are sampled on the input side of the resonant circuit, the high-frequency voltage and high-frequency current can be measured with zero phase difference, and welding power can be calculated with high accuracy using a simple calculation formula. can be measured.

Although this embodiment uses a vacuum tube for the oscillator, the same effect can be obtained even if a semiconductor element such as a power transistor is used.

〔effect〕

As described in detail above, the method for measuring welding power of a high-frequency welding device according to the present invention measures a high-frequency voltage and a high-frequency current that change at high speed over a predetermined period at different points within one cycle of a pulsating voltage applied to a resonant circuit. After sampling and storing the sampled data in the storage device, the stored data is transmitted to the arithmetic device for calculation, so that a general-purpose arithmetic device that performs calculations can be used as the arithmetic device. Furthermore, since the high-frequency voltage and high-frequency current are sampled at different times within one cycle of the pulsating voltage, the peak values of the high-frequency voltage and high-frequency current can be averaged, and the welding power can be measured with high precision. Furthermore, since the high-frequency voltage and high-frequency current are sampled on the input side of the resonant circuit, measurements can be made with the phase difference between them being zero, resulting in excellent effects such as being able to measure welding power with high precision using a simple calculation formula. play.

[Brief explanation of the drawing]

Fig. 1 is a schematic circuit diagram of a high-frequency welding device for carrying out the welding power measurement method according to the present invention, Fig. 2 is a timing chart showing the process from sampling to calculation of high-frequency voltage, and Fig. 3 is a diagram showing the timing chart of the high-frequency welding device for implementing the welding power measuring method according to the present invention. FIG. 4 is a high-frequency voltage waveform diagram for explaining the calculation operation. DESCRIPTION OF SYMBOLS 1... Oscillator, 2... Resonance circuit, 7... High frequency current measuring device, 8... High frequency voltage measuring device, 9...
...Storage device, 10...Arithmetic unit, Pw...Welding power, ep...High frequency voltage, ip...High frequency current.

Claims (1)

[Claims] 1. A method for measuring welding power of a high-frequency welding device that generates a high-frequency oscillator to perform welding, comprising a resonant circuit to provide the output of the oscillator, and a high-frequency voltage and a high-frequency voltage on the input side of the resonant circuit. The current, the pulsating voltage applied to the resonant circuit, and 1
Sampling is performed over a predetermined period at different points in the cycle, the sampled data is stored in a storage device, the stored data is sequentially read out and transmitted to a calculation device, and the calculation device calculates the welding power. Features: A method for measuring welding power of high-frequency welding equipment.